Thermostatic electric switch



Filed Aug. 6, 1932 ll KR i lwam gm 8 INVENTOR L L E H C T Patented Sept. 26, 1933 UNITED STATES THERMOSTATIC ELECTRIC SWITCH Benjamin E. Getchell, Plainville, Conn., assignor to The Trumbull Electric Manufacturing Company, Plainville, Conn., a corporation of Connecticut Application August 6, 1932. Serial No. 627,705

8 Claims.

My invention relates to electric switches actuated automatically upon changes of temperature.

The main object of the invention is to provide a simple but reliable thermostatic switch for opening and/or closing electric circuits with a snap action. I have especially sought to provide a construction which can be made according to uniform standards at reasonable cost and which can be readily adjusted to meet varying conditions of use.

A special object is to provide a snap action mechanism in which the contacts will remain effectively closed until the proper moment for breaking the circuit whereupon the contacts will be separated without any possibility of chatter ingor vibration which would tend to produce arcing or otherwise injure the contacts.

In its preferred form the invention includes a bi-metallic thermostatic strip anchored at one end and having a movable contact arm pivotally hooked to the free or movable end of the strip with a compression spring interposed between the movable end of the strip and a shoulder on the contact arm. A stop element is provided for limiting the movement of the free end of the strip in both directions. An adjusting screw is also preferably provided for the strip and positioned near its anchored end. The relatively stationary contact is preferably adjustable.

The construction is such that when the device is in operation and approaching the moment of separating the contacts in either direction, the spring pressure against the stationary contact increases until the breaking point is actually reached when the-contact arm quickly snaps away from a positive contact position to open the circuit with a snap action. This in contradistinction to other similar devices in which the tendency of the contact is to gradually creep away from the snapping position which results in vibration and hesitating movement of the contact.

In the drawing I have illustrated two forms of construction.

Fig. 1 is a side view showing one form of the invention.

Fig. 2 is an exploded perspective view showing parts of the mechanism of Fig. 1.

Fig. 3 is a front view of one form of construction embodying a modified form of thermostatic strip.

Fig. dis a side view and partial section of the construction shown in Fig. 3.

The conducting parts may be mounted upon an insulating support '7 of any suitable character.

The bi-metallic thermostatic strip 8 is secured to the support in any suitable manner as for instance by means of screws 9. The initial position of the strip 8 may be adjusted by means or" a screw 10. A hook-like member 11 serves to limit the possible swinging movement of the thermostatic strip 8. The movable switch contact arm 12 has a hook-like portion 13 which is connected to a cross bar 14 near the movable end of the thermostatic strip 8. It will be understood of course that the thickness of the strip 8 is considerably exaggerated. The cross bar 14. and the hook member 13 have in eiiect a knife edge connection.

The end of the strip 8 is extended beyond the cross bar or pivot member 14 and provided with a seat or abutment 15 for one end of the spring 16. This spring encircles a part of the contact arm 12 and presses against the shoulder 17. The result is that whenever the strip 8 and the contact arm 12 are the least bit out of alignment, the spring 16 will exert a pressure on the contact arm to snap it with a toggle-like actionto one side or the other of the central plane of the thermostatic strip.

There are two stops 18 and 19 which limit the movement of the end of the contact arm 12. Either one or'both of these stops may constitute the relatively stationary contact. Preferably one of the stops, for instance; the stop 19 is adjustable to permit variation in the distance between the stops. form of a screw and provided with a lock nut 20. It will be understood of course that the stationary and movable contacts will be made of material suitable for such work. When in use a change in temperature will warp or flex the resilient bimetallic or thermostatic strip 8 and thus tend to' bring this strip and the extension contact arm 12 into alignment. A continued change in temperature beyond that suflicient to bring these two members into alignment permits the spring 16 to exert an oil-center pressure on the contact arm 12 and snap it away from the position shown in Fig. 1 where the contact engages the end of the screw 19 and into an effective contact with the stop 18 thus making and/or breaking the circuit, depending upon how the stops are electrically connected. There is therefore none of the tendency of the movable switch member to chatter or vibrate, which is common in other devices of this character. Regulation of the screws 10 and 19 would make it possible to adjust the device to operate at the desired temperature.

In the form of construction shown in Figs. 3 and 4 the thermostatic strip 8' is bowed and has The member 19 is therefore in the its stationary end 21 on the back of the support 7 and adjustable by a screw 10. The construction and mode of operation, however, are otherwise the same as the form shown in Figs. 1 and 2.

The advantages of constructions of this character will be apparent to those skilled in the art.

I claim:

l. A thermostatic switch including a bi-metallic strip adjustably supported at one of its ends and having its other end freely movable, a contact arm detachably hooked to the free end of said strip and having a shoulder, a compression spring on said arm interposed between the shoulder on said arm and the free end of said strip, rigid stop means for said strip in both of its movable directions and relatively stationary stops for said contact arm, at least one of said contact arm stops constituting an electric contact.

2. A thermostatic switch including a lei-metallic thermostatic strip supported at one of its ends and having a freely movable end, means for adjusting the supported end of said strip, a contact arm having a detachably hooked connection with the movable end of said strip, a compression spring interposed between the free end of said strip and the outer end of the contact arm, a stop for the free end of said strip and rigid stops for said contact arm in both of its movable directions, at least one of said contact arm stops being adjustable with respect to the other stop.

3. A thermostatic switch including a bi-metallic strip supported at one of its ends and freely movable at its other end, a cross bar on the movable end of the strip, a contact arm having a hook portion detachably engaged with said cross bar, a compression spring interposed between the free end of said strip and a portion of said contact arm, stop means for said strip and an adjustable stop for at least one of the sides of said contact arm.

4. A thermostatic switch including a bi-metallic strip supported at one end and movable at the other end, means for limiting the movement of the movable end of said strip, a contact arm having one end hinged to the movable end of said strip and provided with a contact at its other end, a relatively stationary contact adapted tobe engaged by the contact end of said arm, and a compression spring interposed between the contact end of said arm and the movable end of said strip.

5. In a thermostatic switch, a bi-metallic strip supported at one of its ends, and having a freely movable end, means for adjusting the position of the supported end of the strip, rigid stop means for the free end of said strip, a contact arm detachably hinged to the strip and having a shoulder, a compression spring interposed between said shoulder and the free end of said strip and adjustable stops for said contact arm, one of said contact arm stops constituting an electric contact.

6. In a thermostatic switch, a bi-metallic thermostatic strip supported at one of its ends and being freely movable at its other end, means for adjusting the supported end of said strip, a contact arm detachably hinged at one end to the movable end of said strip, a compression spring interposed between the free end of said strip and the other end of the contact arm, stops for limiting the movement of the free end of said strip, and stops for limiting the movement of said contact arm, at least one of said stops for said contact arm being adjustable and at least one of said contact arm stops constituting an electric contact.

7. In a thermostatic switch, a bi-metallic strip supported at one of its ends and being freely movable at its other end, stops for limiting the movement of the free end of said strip, a cross bar at the movable end of the strip, a contact arm detachably hinged to said cross bar, a compression spring on said arm interposed between the free end of said strip and a portion of said contact arm and rigid stops for limiting the movement of said contact arm, at least one of said stops for said contact arm being adjustable and at least one of'said stops for said contact arm constituting an electric contact.

8. In a thermostatic switch, a bi-metallic strip supported at one end and movable at the other end, means for limiting the movement of the movable end of said strip, a contact arm having one end hinged to the movable end of said strip and provided with a contact at its other end, a

relatively stationary contact adapted to be en gaged by the movable end of said arm, and a compression spring on said arm interposed between a part of said arm and the movable end of said strip.

BENJAMIN E. GETCHELL. 

